Nature, 27 February 2025, Volume 638 Issue 8052
《自然》2025年2月27日，第638卷，8052期
化学Chemistry
Total synthesis of 25 picrotoxanes by virtual library selection
通过虚拟库筛选实现25种木防己苦毒素化合物的全合成
▲ 作者：Chunyu Li (李春雨) Ryan A. Shenvi
▲ 链接：articles/s41586-024-08538-y
▲摘要：为了解决问题且避免繁琐的试错实验，我们构建了一个虚拟库，其中包含难以捉摸的后期中间体类似物，这些类似物通过反应性进行筛选并改变了合成路径。该方法的效率促成了25种天然木防己苦毒素化合物的简化合成路线。
昂贵的密度泛函理论过渡态计算被更快的反应物参数化所取代，从而提高了可扩展性，并在本研究中揭示了反应机制。这种方法可以作为人类或计算机辅助合成规划的附加搜索工具，适用于高复杂性目标化合物和/或文献或反应数据库中代表性不足的步骤。
▲ Abstract：Here, to solve this problem but avoid tedious guess-and-check experimentation, we built a virtual library of elusive late-stage intermediate analogues that were triaged by reactivity and altered the synthesis pathway. The efficiency of this method led to concise routes to 25 naturally occurring picrotoxanes. Costly density-functional-theory transition-state calculations were replaced with faster reactant parameterizations to increase scalability and, in this case, inform the mechanism. This approach can serve as an add-on search to human or computer-assisted synthesis planning applicable to high-complexity targets and/or steps with little representation in the literature or reaction databases.
古人类学Paleoanthropology
Ancient DNA reveals reproductive barrier despite shared Avar-period culture
古代DNA揭示阿瓦尔时期存在生殖隔离
▲ 作者：Ke Wang, Bendeguz Tobias et al.
▲ 链接：articles/s41586-024-08418-5
▲摘要：公元567至568年，具有东亚血统的阿瓦尔人经过长途迁徙抵达了东中欧，并与具有欧洲血统的群体相遇。我们利用722个个体的古代全基因组数据，并结合对维也纳南部两处大型七至八世纪相邻墓地的精细跨学科分析，探讨这一相遇在数百年间的影响。
我们发现，即使在200年后，一处遗址（莱奥贝斯多夫）的血统仍以东亚为主，而另一处遗址（默德林）则显示出本地欧洲血统。尽管这两处相邻遗址共享独特的晚期阿瓦尔文化，但它们之间的生物学亲缘关系却非常有限。我们重建了两处遗址的六代家谱，涵盖多达450名近亲个体，从而对社区进行逐代人口统计分析。
尽管血统不同，但这些家谱以及广泛的远亲关系网络显示，近亲繁殖现象不存在，父系模式与女性外婚制并存，存在多重生殖伙伴关系（如娶寡嫂制），并且生物学连通性与社会地位的考古标记直接相关。这种代际遗传屏障的维持，是通过系统性地选择来自阿瓦尔领域内其他遗址的具有相似血统的伴侣实现的。
莱奥贝斯多夫与阿瓦尔核心地区的生物学联系比与默德林更为紧密，而默德林则与维也纳盆地的另一处具有欧洲血统的遗址相关联。遗址之间的流动性主要源于女性外婚制，表明不同的婚姻网络是维持遗传屏障的主要驱动力。
▲ Abstract：After a long-distance migration, Avars with Eastern Asian ancestry arrived in Eastern Central Europe in 567 to 568 CE and encountered groups with very different European ancestry. We used ancient genome-wide data of 722 individuals and fine-grained interdisciplinary analysis of large seventh- to eighth-century CE neighbouring cemeteries south of Vienna (Austria) to address the centuries-long impact of this encounter. We found that even 200?years after immigration, the ancestry at one site (Leobersdorf) remained dominantly East Asian-like, whereas the other site (M?dling) shows local, European-like ancestry. These two nearby sites show little biological relatedness, despite sharing a distinctive late-Avar culture. We reconstructed six-generation pedigrees at both sites including up to 450 closely related individuals, allowing per-generation demographic profiling of the communities. Despite different ancestry, these pedigrees together with large networks of distant relatedness show absence of consanguinity, patrilineal pattern with female exogamy, multiple reproductive partnerships (for example, levirate) and direct correlation of biological connectivity with archaeological markers of social status. The generation-long genetic barrier was maintained by systematically choosing partners with similar ancestry from other sites in the Avar realm. Leobersdorf had more biological connections with the Avar heartlands than with M?dling, which is instead linked to another site from the Vienna Basin with European-like ancestry. Mobility between sites was mostly due to female exogamy pointing to different marriage networks as the main driver of the maintenance of the genetic barrier.
地球科学Earth Science
Continued Atlantic overturning circulation even under climate extremes
大西洋经向翻转环流在极端气候下仍然持续
▲ 作者：J. A. Baker, M. J. Bell et al.
▲ 链接：articles/s41586-024-08544-0
▲ 摘要：我们展示了大西洋经向翻转环流（AMOC）在34个气候模型中对极端温室气体和北大西洋淡水强迫表现出适应性。由持续的南大洋风驱动的南大洋上升流维持了AMOC的减弱状态，防止其完全崩溃。
由于南大洋上升流必须通过大西洋或太平洋的下沉流来平衡，因此只有在补偿性的太平洋经向翻转环流（PMOC）发展时，AMOC才可能崩溃。值得注意的是，几乎所有模型中都出现了PMOC，但其强度不足以平衡所有南大洋上升流，这表明本世纪AMOC崩溃的可能性较低。
我们的研究揭示了AMOC的稳定机制，这些机制对过去和未来的AMOC变化具有重要意义，进而对生态系统和海洋生物地球化学产生影响。
研究还表明，迫切需要更好地理解和评估南大洋和印度—太平洋环流，以准确预测未来AMOC的变化。
▲ Abstract：Here we show that the The Atlantic Meridional Overturning Circulation (AMOC) is resilient to extreme greenhouse gas and North Atlantic freshwater forcings across 34 climate models. Upwelling in the Southern Ocean, driven by persistent Southern Ocean winds, sustains a weakened AMOC in all cases, preventing its complete collapse. As Southern Ocean upwelling must be balanced by downwelling in the Atlantic or Pacific, the AMOC can only collapse if a compensating Pacific Meridional Overturning Circulation (PMOC) develops. Remarkably, a PMOC does emerge in almost all models, but it is too weak to balance all of the Southern Ocean upwelling, suggesting that an AMOC collapse is unlikely this century. Our findings reveal AMOC-stabilizing mechanisms with implications for past and future AMOC changes, and hence for ecosystems and ocean biogeochemistry. They suggest that better understanding and estimates of the Southern Ocean and Indo-Pacific circulations are urgently needed to accurately predict future AMOC change.
Warming and cooling catalyse widespread temporal turnover in biodiversity
变暖与降温催化了生物多样性的广泛时间更替
▲ 作者：Malin L. Pinsky, Helmut Hillebrand et al.
▲ 链接：articles/s41586-024-08456-z
▲摘要：我们分析了来自海洋、陆地和淡水群落的42225个物种组成的时间序列。结果表明，在经历更快温度变化（包括变暖和降温）的地点，时间更替率始终更快。
此外，那些难以进入微气候避难所或面临更强人类影响的陆生群落对温度变化尤为敏感，每十年物种更替率高达48%。
这些结果揭示了对持续气候变化的广泛脆弱性信号，并突出了哪些生态群落最为敏感，从而引发了对生态系统完整性的担忧，因为气候变化和其他人类影响正在加速。
▲ Abstract：Here we analyse 42,225 time series of species composition from marine, terrestrial and freshwater assemblages, and show that temporal rates of turnover were consistently faster in locations that experienced faster temperature change, including both warming and cooling. In addition, assemblages with limited access to microclimate refugia or that faced stronger human impacts on land were especially responsive to temperature change, with up to 48% of species replaced per decade. These results reveal a widespread signal of vulnerability to continuing climate change and highlight which ecological communities are most sensitive, raising concerns about ecosystem integrity as climate change and other human impacts accelerate.
生物学Biology
Widespread occurrence and relevance of phosphate storage in foraminifera
磷酸盐在有孔虫中储存的广泛性及相关性
▲ 作者：Nicolaas Glock, Julien Richirt et al.
▲ 链接：articles/s41586-024-08431-8
▲ 摘要：我们展示了磷酸盐储存在有孔虫中是广泛存在的，从潮滩到深海均有发现。在瓦登海里，底栖有孔虫Ammonia confertitesta在水华期间细胞内储存的磷酸盐总量高达德国每年磷肥消耗量的约5%。对南北海和秘鲁氧最小区的预算计算表明，底栖有孔虫可能在南北海缓冲河流磷径流约37天，在秘鲁边缘缓冲约21天。
这表明这些生物可能对海洋磷循环具有重要意义——它们可能在沿海环境中为人为富营养化的情况进行缓冲。磷酸盐以多聚磷酸盐的形式储存在细胞器中，这些细胞器可能是酸性钙化体。
它们的代谢功能可能包括调节渗透压、细胞内pH值以及钙和能量储存。此外，储存高能磷化合物（如磷酸肌酸和多磷酸）可能是有孔虫对氧气耗竭的一种适应机制。
▲ Abstract：Here we show that phosphate storage in foraminifera is widespread, from tidal flats to the deep sea. The total amount of intracellular phosphate stored in the benthic foraminifer Ammonia confertitesta in the Wadden Sea during a bloom is as high as around 5% of the annual consumption of phosphorus (P) fertilizer in Germany. Budget calculations for the Southern North Sea and the Peruvian Oxygen Minimum Zone indicate that benthic foraminifera may buffer riverine P runoff for approximately 37?days at the Southern North Sea and for about 21?days at the Peruvian margin. This indicates that these organisms are probably relevant for marine P cycling—they potentially buffer anthropogenic eutrophication in coastal environments. Phosphate is stored as polyphosphate in cell organelles that are potentially acidocalcisomes. Their metabolic functions can range from regulation of osmotic pressure and intracellular pH to calcium and energy storage. In addition, storage of energetic P compounds, such as creatine phosphate and polyphosphate, is probably an adaptation of foraminifera to O2 depletion.
Learned magnetic map cues and two mechanisms of magnetoreception in turtles
海龟学习磁地图的线索与两种磁感应机制
▲ 作者：Kayla M. Goforth, Catherine M. F. Lohmann et al.
▲ 链接：articles/s41586-024-08554-y
▲摘要：长期以来，人们一直认为，动物要利用地磁地图进行导航，必须了解目的地的地磁坐标。然而，关于动物能够学习地理区域地磁特征的关键假设尚未得到验证。
我们报告一种标志性的导航物种——红海龟（Caretta caretta）能够学习此类信息。当在模拟特定海洋位置地磁场的磁场中被反复喂食时，幼年海龟学会了区分它们遇到食物的磁场与其他地方的磁场，这种能力可能是其觅食地点忠诚性的基础。
在这种新的地磁地图测试中，条件反射不受射频振荡磁场的影响，而射频振荡磁场应该会破坏基于自由基对的化学磁感受机制，这表明海龟的地磁地图感知并不依赖这种机制。相比之下，需要利用磁罗盘的定向行为则会被射频振荡磁场干扰。这些发现提供了证据，表明海龟的地磁地图和“磁罗盘”依赖于两种不同的磁感应机制。
▲ Abstract：It has long been proposed that, to navigate using a magnetic map, animals must learn the magnetic coordinates of the destination, yet the pivotal hypothesis that animals can learn magnetic signatures of geographical areas has, to our knowledge, yet to be tested. Here we report that an iconic navigating species, the loggerhead turtle (Caretta caretta), can learn such information. When fed repeatedly in magnetic fields replicating those that exist in particular oceanic locations, juvenile turtles learned to distinguish magnetic fields in which they encountered food from magnetic fields that exist elsewhere, an ability that might underlie foraging site fidelity. Conditioned responses in this new magnetic map assay were unaffected by radiofrequency oscillating magnetic fields, a treatment expected to disrupt radical-pair-based chemical magnetoreception, suggesting that the magnetic map sense of the turtle does not rely on this mechanism. By contrast, orientation behaviour that required use of the magnetic compass was disrupted by radiofrequency oscillating magnetic fields. The findings provide evidence that two different mechanisms of magnetoreception underlie the magnetic map and magnetic compass in sea turtles.
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